Norway is a country where avalanches are a very common nature phenomenon, and accidents caused by avalanches have always been a problem for Norwegian roads. The public roads administration has through the last years dimensioned and designed many different protections against avalanches. Later, investigations have showed that the avalanche protections several times have not satisfied the requirements for the effect of avalanche protection. Low effect of the avalanche protection can reduce the risk level at the avalanche exposed road sections. Through cooperation with the public roads administration (Vegdirektoratet and Region Nord), 8 avalanche protection facilities distributed in Nordland, Troms and Finnmark, were chosen with purpose to evaluate different factors which can reduce the effect of the avalanche protections.

In this evaluation, factors like the quality of the avalanche protection plan for the different roadsections, if the avalanche protection was dimensioned after the guidelines, if there was deviation between the original plan and finished work for the avalanche protection, were considered. In addition, the effects of avalanche protection seen from the side of the road user and maintenance were also evaluated. From inspections and collected material from different facilities, avalanche protection like snow sheds (galleries), snow fences, catching dams, deflecting berms, sea&nbsp; filling, and wide ditch, were evaluated.

The quality of the avalanche protection plan:

The results show several times that the avalanche protection plan has to bad quality with a view it shall be used in the planning stage of an avalanche protection facility. The suggestion to protection method in the avalanche protection plan has several times not been followed. In the cases where the plan actually has been followed the results show that the current avalanche protection in later times where repaired or changed to reach a greater risk level.

Too little stress on preliminary investigations of the avalanche area is probably one of the reasons that can cause reduced quality of the avalanche protection plan. To reach a greater quality it has been suggested to do more investigations of the starting zone characteristics, the avalanche distribution, different typesof avalanches, the avalanche frequency in each track, and what risk level the avalanche protections should obtain.

Possible deviations in proportion to the design guidelines:

The results show that most of the avalanche protection facilities contain avalanche protection that are not dimensioned after the recommendations in the design guidelines.

In the calculations of forces from avalanches on the snow sheds(galleries), the results show that the public road administration probably have dimensioned with lower diversion forces than the recommendations in the Swiss design guidelines. Further, the drainage system connected to the snow sheds is in several cases not protected against erosion as recommended in the guidelines. In addition, several deflecting berms have not satisfied the deflection angle in proportion to the avalanche flow direction, and are built with too high percentage of fine-graded materials. The results also show that the deflecting berms will have reduced effect against the avalanche motion in steep terrain. In this exercise, the design height of several of the catching dams which were investigated was not high enough based on the design guidelines to satisfy the risk level.

Among other things it has been suggested that the slope on the uphill side of the catching dam shouldbe built as steep as economically possible with dry wall or geotextile. The steep slope on the uphill sidewill take out more energy from the avalanche.

Deviation between finished work and the original plan for the avalanche protection:

Most of the avalanche protections have deviation between the original plan for the avalanche protection and finished work. The results show that the deviations have aroused in the planning stage or in the building stage of the avalanche protection facility. The most common reason for these deviations is insuffcient preliminary investigation of problems connected to water and ground condition, and not so good quality of the building plans. The results show that it is especially important with good investigations of problems connected to water and ground condition in cases where snow sheds shall be built in areas with much moraine and avalanche deposits. To reach greater quality of the building plans, especially for catching dams, it has been suggested that design height, slope angles, and dimensions of the catching area should be showed in the building plan.

The effect of the avalanche protection seen from road user and maintenance:

Several of the avalanche protections have reduced effect seen from the side of the road user and maintenance.The results show that the drainage system many times doesn't have good enough protection against erosion, and are not steep enough to get a sufficient drainage. This will increase the avalanche protections need for maintenance. Further, most of the snow fences are not accessible for maintenance because of a distant location. The results also show that the soil in slopes and deflecting berms over the entrance to the snow sheds can fall down on the road. In addition, several of the snow sheds have problems connected to water accumulation on the roads inside the galleries.

To avoid downfall from the slopes/deflecting berms over the entrance to the snow sheds, it has been suggested to build the deflecting berms with dry walls to make the slopes 90 degrees, if this is possible regarded to economic and engineering issues. This can avoid downfall of loose material connected to erosion processes, and avoid cornices to grow up on the leeward side of the slope.